This invention relates to vehicle speed controls and more particularly to such controls using electronic logic and fluid powered actuating means.
Vehicle speed controls have been known for some time and have been widely accepted. Because of their economics, reliability and accuracy, fluid actuated speed controls have become the dominant factor in this market. Such controls typically use vacuum from the vehicle engine manifold as the actuating force. The vacuum is applied to a bellows connected to the throttle linkage and thereby increases or decreases the throttle position to advance or retard the vehicle speed. The control for such a system compares actual vehicle speed with desired vehicle speed and adjusts the vacuum level in the bellows accordingly. Typically, the control is via a continuous modulated bleed of atmospheric air into the bellows. Such a bleed looks, to the engine, like a leak in the manifold gasketing and is somewhat detrimental to engine performance. This has not been a major problem in the past when typical vehicles having speed controls used large engines and were tuned in a range which allowed relatively wide latitude in fuel/air ratio.
Recently the average size of engines in vehicles equipped with speed controls has been decreasing. In addition engine tuning has been modified toward lean fuel/air ratios. Both of these factors have made it more critical to limit the amount of atmospheric bleed reaching the engine manifold. Because of their simplicity and wide acceptance, however, it remains desirable to use speed controls having operators utilizing engine vacuum for actuation.
Accordingly, it is an object of this invention to provide a vacuum actuated vehicle speed control which effects a minimum atmospheric bleed to the vehicle engine manifold.
It is a further object to provide such a speed control which is accurate to the high standards of previous units.
It is still a further object to provide such a speed control which includes a plurality of convenience and safety features for safe simple operation.